The present invention relates to a developing device incorporated in a copier for feeding a toner from a toner container to a liquid reservoir to thereby supply a toner-containing liquid developer to a developing unit.
A developing device of the type described is disclosed in, for example, Japanese Utility Model Application No. 333362/1990, and has a liquid reservoir, a toner container, actuating means for toner supply, and developer feeding means. The toner container has a container body filled with a toner, and discharging means for discharging the toner to the outside of the container body via a nozzle in association with an action for toner supply effected at the outside. The actuating means operates the discharging means. The developer feeding means is disposed in the liquid reservoir for feeding the toner-containing liquid developer to a developing unit. The device supplies the toner via the nozzle of the toner container until the toner in the liquid reaches a predetermined concentration, while sensing the toner concentration by a concentration sensor.
One of conventional toner containers has a first chamber to be inflated by a gas, and a second chamber storing a toner therein and contracting when the first chamber inflates, as taught in Japanese Utility Model Laid-Open Publication No. 125457/1989. However, this kind of toner container has various problems, as follows. The container body has to be implemented as a pressure container resistive to a pressure of 15 kilograms per square centimeter. It is necessary to use furon gas or similar toxic gas which pollutes the environment. Since the wet toner contains an organic solvent, the toner container is apt to burst when thrown into fire. In addition, an extra step is needed to check the crimped portion of valve means as to the leakage of the toner, increasing the cost of the toner container.